Stress is an adaptive strategy that mobilizes the body for acute physical challenges, but chronic stress has detrimental effects. Thus, coping mechanisms are valuable in reducing stress. One such mechanism, the “tend-and-befriend” strategy, refers to affiliation between females as an adaptive strategy to deal with the effects of elevated stress after fight-or-flight situations. This mechanism is proposed to be a widespread strategy throughout the primate order, and one that underlies patterns of female bonding in humans. Although this strategy is utilized by matrilineal primates characterized by female kinship bonds, there has not been documentation of this strategy among unrelated females. Here, I examine the relationship between female affiliation and cortisol concentrations in 11 wild female black-handed spider monkeys. Time spent affiliating with females is significantly positively correlated with mean cortisol concentrations (rs=0.829, p=0.002, df=11). Time spent huddling (rs =0.780, p=0.005), grooming (rs =0.800, p=0.003) and playing (rs =0.753, p=0.007) with other females are all positively correlated with mean cortisol concentrations. Contrary to predictions, females that spend the most time affiliating with other females have the highest cortisol concentrations. However, in a separate validation study on a captive population, I found that cortisol peaks in feces 24 hours after a stressor. In my study of wild females, both fecal samples and behavioral data were usually collected on the same day. Thus the high cortisol of affiliating females suggests that females are using social interactions as a way of ameliorating spikes in cortisol concentrations. Female spider monkeys do appear to tend-and-befriend.

This research was funded by the Wenner Gren Foundation, the American Philosphical Society Lewis and Clark Fund, and The Ohio State University Alumni Grant.